The present invention relates to improvements in coupling members for connecting flanged duct ends.
In particular, it relates to an improvement in the duct connector disclosed in U.S. Pat. No. 4,461,499 to Hunter et al entitled "Transverse Joint System for sheet Metal Ducts", the entire disclosure of which is incorporated herein by reference. That patent is assigned to the assignee of the present application, and it depicts a system for connecting sheet metal duct sections. That system has proven to be very useful over the years. It includes flanging the ends of sheet metal ducts, abutting them at an interface and forming a plurality of spaced tabs in the wall surface of the flanges, which tabs protrude outwardly in a direction away from the interface. A generally V-shaped coupling member having sidewalls with free edges folded back under the corresponding side wall is then assembled over a pair of abutted flanges, with the edges of the folded under portions snapping in behind the tabs to lock the flanges together. Such V-shaped coupling members are arrayed around the periphery of the duct and, at their intersection, are interleaved. The coupling members are secured by drilling the interleaved portions and joining them with a nut and bolt arrangement.
The present invention focuses on improving the coupling member so that when it couples the flanged ends of the ducts together, the joint has a greater strength than the coupling member of the aforementioned patent. The coupling member of the present invention may also be used as a reinforcement of a duct side wall, spaced from the joint, as disclosed in my copending application entitled "Duct Reinforcement", Ser. No. 819,405, filed Jan. 10, 1992. The invention may also be configured to be used in conjunction with corner pieces as described in my copending application entitled "Corner Pieces for Improved Duct Connector", Ser. No. 818,848 filed Jan. 10, 1992 herewith. The disclosures of the two aforementioned applications are incorporated herein by reference.
The strength of the joint provided by the coupling member as described in my prior patent is adequate for most circumstances, however, when very large cross section ducts are to be joined, additional reinforcement is desirable to prevent sagging, bowing and bulging caused by high inner pressures. While other reinforcement means are known, including applying angle irons to the outside of the ducts, the installation of those angle irons in addition to the installation of the coupling member adds labor and parts expense. Thus, it would be advantageous if these expenses could be avoided.